If successful, the proposal would lead to the first-ever rules aimed at carbon emissions from existing power plants.

States would have broad latitude in terms of how to meet a carbon standard, according to The New York Times and The Wall Street Journal, which first reported the preview of the rule on Sunday.

Options could include joining or starting a cap and trade program, which sets limits on emissions and then allows for the purchase and sale of pollution permits; boosting the share of renewable energy in electricity generation; and tightening efficiency standards.

The proposed rules come nearly a month after a sweeping national climate assessment that catalogued a range of impacts already occurring as a result of climate change.

Reducing